R/file.handler.R

In roverrobot/make: Make utility in R

#' this class defines a general interface for handling a file
FileHandler <- R6::R6Class(
  "FileHandler",
  public = c(
    # the list of file extensions that this handler can handle
    pattern = "",
    #' check if handler can handle the given file
    #' @param file the file to run
    #' @return logical, TRUE if it can run, FALSE if it cannot.
    canHandle = function(file) {
      return(match.stem(self$pattern, file))
    }
  )
)

#' defines a file handler manager
Manager <- R6::R6Class(
  "Manager",
  private = list(
    #' the list of file handlers to manage
    handlers = list(),
    #' the class of handlers that it managers
    class = NULL
  ),
  public = list(
    #' get a handler that can handle a file
    #' @param file, the name of a file to search for a handler
    #' @return a handler
    get = function(file) {
      for (i in private$handlers)
        if (i$canHandle(file)) return(i)
      return (NULL)
    }
    ,
    #' add  a handler to the first of the list of handlers
    #' @param handler a file handler
    add = function(handler) {
      if (!is(handler, private$class))
        stop("The interpreter must be an object of ", private$class)
      private$handlers <- c(list(handler), private$handlers)
    }
    ,
    #' initializer
    initialize = function(class) {
      private$class <- class
      private$handlers <- list()
    }
  )
)

#' scans for dependences of a file
Scanner <- R6::R6Class(
  "Scanner",
  inherit = FileHandler,
  public = list(
    #' scan a file for dependences
    #' @param file the file to scan
    #' @return a vector of dependences, or c() if none
    scan = function(file) {
      c()
    },
    #' initializer
    initialize = function(pattern) {
      self$pattern <- pattern
      scanners$add(self)
    }
  )
)

scanners <- Manager$new(class="Scanner")